Circuit Description - Kenwood TR-7625 Service Manual

TR-7625
CIRCUIT DESCRIPTION
1. Phase Locked Loop
Rx Tx Freq. | Simplex Output Osc Xtal Freq. IF Freq.
144.00 MHz 133.3 MHz 43.7667 MHz 2 MHz
134.3 MHz 3 MHz 43.7667 MHz
145.00 MHz
145.99 MHz} 135.29 MHz 399 43.7667 MHz 3.99 MHz
135.3 MHz 200 44.4333 MHz 2 MHz
146.00 MHz
44.4333 MHz 3 MHz
147.00 MHz 136.3 MHz
137.29 MHz 44.4333 MHz 3.99 MHz
147.99 MHz
Table 1 Division and Frequency
2. +5 kHz Circuit
In the PLL circuit, the reference frequency is controlled
in 10 kHz steps.
The +5
kHz signal is controlled by
varying
the
local oscillator
crystal frequency
vari-cap
diode, so the frequency division remains unchanged
even when the +5 kHz circuit is operated.
The memory circuit also includes the same bit and func-
tions even when the +5 kHz circuit is operating.
3. Shift Circuit
Transmit frequencies can be shifted by changing the
local oscillator crystal frequency, as shown
below.
144 and 145 MHz bands:
The [+] shift is not available for 144 and 145 MHz
bands, [S] occurs at the [+] position.
146 and 147 MHz Bands:
[—] shift 44.2333 MHz
[+] shift 44.6333 MHz
(s] 44,4333 MHz
4. Memory Shift Circuit
The memory shift (M) is a circuit to shift to the memory
frequency during transmission.
CONTROL UNIT
Frequency settings are accomplished by the MHz, 100 kHz
and 10 kHz rotary switches. The relationship between the
frequency and frequency division is shown below.
Frequency Frequency division
144,000 MHz 200
145.000 MHz 300
145.990 MHz 399
146.000 MHz 200
147.000 MHz 300
147.990 MHz 399
The local oscillator kHz order frequency can be (switch)
shifted. Frequency division, set by the rotary switch, is stored
in the latch IC's 1, 2 and 3 by pressing the memory input
switch. The output from the latch circuit is fed through .IC's
4,5 and 6 in the selector circuit to the PLL circuit by pressing
the memory call switch. When this switch is not pressed, the
output is fed directly to the PLL circuit. Memory function Is
effected by latching each switch: The information from each
switch is stored by pressing the memory switch.
The stored information remains the same unless the memory
switch is pressed once again. Selection of memory output
and rotary output is accomplished by the selector circuit. A
latched output is obtained by pressing the memory output
switch.
The signal to the PLL circuit passes through the LED driver
circuit and is digitally indicated by LED.
baton
164035 BP x3
MEMORY
swiTCH
SELECTOR
Te 4019 OF
SYNTHESIZE BCO CORD OUTPUT
O MEMORY OUTPUT
Fig. 2 Block Diagram of Frequency Memory Circuit
© ROTARY Switch ovrpur *